Diode Laser System Research Articles

Metal Cutting with Multi kW Diode Laser

AbstractCutting roughness lower than 10 μm and a wall‐plug efficiency of 30% including cooling are two nameable advantages when speaking about direct diode laser cutting of metals. Emphasizing in this context “direct diode laser” stress that metal cutting with a diode laser is not a conventional process. However, steady developments in diode bar technology enabled the design of a high brightness diode laser system with 2 kW output power and a beam parameter product of 22 mm*mrad. This now commercially available “DIOCUT” system is ready to enter the laser macro cutting market. The applicability of this system is demonstrated by cutting aluminum, stainless steel, copper and mild steel. The cutting edge quality is comparable with CO2 laser cuts. On our roadmap is higher output power at equal beam quality in near future.

Dual-wavelength high-power diode laser system based on an external-cavity tapered amplifier with tunable frequency difference

A dual-wavelength high-power semiconductor laser system based on a tapered amplifier with double-Littrow external cavity is demonstrated around 800 nm. The two wavelengths can be tuned individually, and the frequency difference of the two wavelengths is tunable from 0.5 to 10.0 THz. To our knowledge, this is the broadest tuning range of the frequency difference from a dual-wavelength diode laser system. The spectrum, output power, and beam quality of the diode laser system are characterized. The power stability of each wavelength is measured, and the power fluctuations of the two wavelengths are almost of opposite phase. The simultaneous emission of the two wavelengths is verified by a sum-frequency generation experiment in a bismuth triborate nonlinear crystal.

The Art of Fetoscopy: A Step Toward Minimally Invasive Fetal Therapy

To study the feasibility, learning curve, and safety of fetoscopy, so that fetal surgery can be confidently performed in ongoing pregnancies. Fetoscopy was performed at 12-20weeks of gestation, in 12 women with fetal congenital malformations and/or for termination of pregnancy, under local anesthesia using fine fetoscopes ranging from 1 to 2-mm diameter. The fetal parts and placenta were examined for clarity of vision, identification, and anomalies. Fetoscopy required great skill, patience, and extensive use of ultrasound for correct orientation. Visualization was better with endoscope of 2-mm diameter. Laser coagulation of placental vessels using diode laser system was possible in the last two cases. There were no major complications. Fetal endoscopy is a feasible procedure, safe in experienced hands but has an appreciable learning curve.

Intraindividual comparison of 1,470 nm diode laser versus carbon dioxide laser for tonsillotomy: A prospective, randomized, double blind, controlled feasibility trial

The need for reduction of post-tonsillectomy hemorrhage has led to promotion of tonsillotomy techniques for tonsil tissue reduction in obstructive tonsillar hypertrophy. This trial compares ablative tissue effects using 1,470 nm diode laser and carbon dioxide laser for tonsillotomy in an intraindividual design. 21 children aged 3-13 years (mean age 6.3 years) underwent laser tonsillotomy for obstructive tonsillar hypertrophy in this double blind, prospective, randomized, clinical feasibility trial. In each of the blinded patients, tonsillotomy was performed using fiber guided 1,470 nm diode laser (contact mode, 15 W power) on the one side and carbon dioxide laser (12 W power) on the other side. An independent, blinded physician documented clinical presentation and patients' symptoms preoperatively and on Days 1, 3, 7, 14, and 21 post-operatively using standardized questionnaire including VAS for each side separately. The mean duration of operative treatment was 2.7 min using 1,470 nm laser and 4.9 min using carbon dioxide laser respectively. Intraoperative bleeding and the frequency of bipolar forceps use for intraoperative bleeding control was significantly less using 1,470 nm diode laser system. There was no difference in post-operative pain scores between the carbon dioxide laser treated and the 1,470 nm fiber guided diode laser treated side. No infections, hemorrhages or other complications occurred in the course of the 3 weeks post-operative period. A fiber-guided 1,470 nm diode laser system offers an efficient and safe method for tonsillotomy as treatment of obstructive tonsillar hypertrophy. Compared to our standard practice (carbon dioxide laser), 1,470 nm laser application provides comparable tissue ablation effects with less intraoperative bleeding and shorter operation time.

Narrow linewidth laser system realized by linewidth transfer using a fiber-based frequency comb for the magneto-optical trapping of strontium

A narrow linewidth diode laser system at 689 nm is realized by phase-locking an extended cavity diode laser to one tooth of a narrow linewidth optical frequency comb. The optical frequency comb is phase-locked to a narrow linewidth laser at 1064 nm, which is frequency stabilized to a high-finesse optical cavity. We demonstrate the magneto-optical trapping of Sr using an intercombination transition with the developed laser system.

High passive-stability diode-laser design for use in atomic-physics experiments

We present the design and performance characterization of an external-cavity diode-laser system optimized for high stability, low passive spectral linewidth, low cost, and ease of in-house assembly. The main cavity body is machined from a single aluminum block for robustness to temperature changes and mechanical vibrations, and features a stiff and light diffraction-grating arm to suppress low-frequency mechanical resonances. The cavity is vacuum sealed, and a custom-molded silicone external housing further isolates the system from acoustic noise and temperature fluctuations. Beam shaping, optical isolation, and fiber coupling are integrated, and the design is easily adapted to many commonly used wavelengths. Resonance data, passive-linewidth data, and passive stability characterization of the new design demonstrate that its performance exceeds published specifications for commercial precision diode-laser systems. The design is fully documented and freely available.

An external cavity diode laser using a volume holographic grating

This study presents an external cavity diode laser (ECDL) system, utilizing a volume holographic grating (VHG) and a microfabricated silicon flexure as the VHG holder. The laser design is aimed for easy assembly, controllability, and better stability of the laser cavity. The laser frequency was stabilized to a D2 transition of rubidium at 780.247nm, with a mode-hop-free tuning range of 16GHz and 9.6GHz with and without feed-forward on the diode injection current. The measured linewidth was 850kHz in 500s, qualified for laser cooling experiments.

Ultra-Narrow Laser for Optical Frequency Reference

We present ultra-narrow line width, tunable diode laser system which will be used as a local oscillator in an optical atomic clock and for precision spectroscopy of Sr near 689 nm. Design of the high nesse optical cavity used as short-term frequency reference is optimized with respect to insensitivity to vibrations. We achieved laser line width of about 8 Hz, measured by comparison of two identical systems. The relative phase lock of two lasers is better than 150 mHz. Laser tunability and usefulness for precison spectroscopy were demonstrated through line shape measurement of a 20 kHz wide resonance of the optical cavity.

Naturally grown Ag nanoparticles on quartz substrates as SERS substrate excited by a 488 nm diode laser system for SERDS

A silver nanoparticle ensemble was prepared under ultrahigh vacuum (UHV) conditions by Volmer–Weber growth on a quartz substrate for surface-enhanced Raman scattering (SERS) investigations of pyrene molecules. To tune the surface plasmon resonance frequency in the vicinity of the excitation wavelength of 488 nm of the diode laser, the morphology of the silver nanoparticles was optimized. The substrates were mounted in a flow-through cell as part of the optical Raman set-up. A microsystem diode laser generates two slightly different emission wavelengths (λ=487.61 nm and λ=487.91 nm) with a spectral width <10 pm and an optical power of 20 mW, i.e. SERS experiments are possible but also shifted excitation Raman difference spectroscopy (SERDS) can be carried out. For trace analysis of pyrene in water we demonstrate SERS/SERDS experiments which lead to a limit of detection of 2 nmol/l for pyrene. These results suggest that with silver nanoparticle ensembles excited at their plasmon resonance at 488 nm combined SERS/SERDS measurements can be effectively performed for in-situ trace analysis of pollutant chemicals in water.

A phase I study of salvage photodynamic therapy (PDT) using talaporfin sodium and a diode laser for local failure of esophageal carcinoma (EC) after chemoradiotheapy (CRT).

123 Background: We recently reported that porfimer sodium (Photofrin)-based PDT was a less invasive, curative treatment option for carefully selected patients with locally residual EC after CRT (Endoscopy 2011:43:657-63). However, porfimer sodium-based PDT has some problems (long light shielding and skin phototoxicities). Conversely, talaporfin sodium (Laserphyrin)-based PDT using a diode laser system can overcome these problems. Therefore, we conducted a phase I study to establish the recommended dose of laser irradiation and to evaluate safety of talaporfin sodium-based PDT as a salvage treatment after CRT. (UMIN000003970). Methods: We recruited patients with residual or recurrent EC at primary site and who were treated with more than 50 Gy of (chemo)radiotherapy. To determine the dose limiting toxicity (DLT) according to the energy of the diode laser, dose escalation was set at three energy levels (50,75 and 100J/cm2). The DLT was defined as follows; 1) severe pain, 2) ≥ grade 2 CTC-AE fever, 3) esophageal fistulae or stenosis, 4) ≥ grade 3 CTC-AE hemorrhage, and 5) ≥ grade 4 CTC-AE non-hematologic toxicity. Results: Between Oct. 2010 and May 2011, a total of 9 patients (9 men, median age of 72 y-o) were recruited and were treated using up to the third energy level in groups of three individuals. The initial T stage was T1/T2/T3(4/2/3) and recurrent T stage was T1/T2(6/3). None of the patients experienced DLT at all energy levels. A complete response was achieved in 5 of 9 patients (56%). Conclusions: Based on the results of our phase I study, we concluded that irradiation at 100J/cm2 appeared to be a recommended dose for talaporfin sodium-based PDT as a salvage treatment for locally residual esophageal carcinoma after CRT. We are currently running a phase II part of the study to investigate efficacy of salvage talaporfin sodium-based PDT.

In Vitro Photothermal Destruction of Cancer Cells Using Gold Nanorods and Pulsed‐Train Near‐Infrared Laser

We present a novel pulsed‐train near‐IR diode laser system with real‐time temperature monitoring of the laser‐heated cancer cell mixed in gold nanorod solution. Near‐IR diode laser at 808 nm matching the gold nanorod absorption peak (with an aspect ratio about 4.0) was used in this study. Both surface and volume temperatures were measured and kept above 43°C, the temperature for cancer cells destruction. The irradiation time needed in our pulsed‐train system with higher laser fluence for killing the cancel cells is about 1–3 minutes, much shorter than conventional methods (5–10 minutes). Cell viabilities in gold nanorod mixed and controlled solutions are studied by green fluorescence.

Reliable Operation for 14500 h of a Wavelength-Stabilized Diode Laser System on a Microoptical Bench at 671 nm

Reliability tests for wavelength-stabilized compact diode laser systems emitting at 671 nm are presented. The devices were mounted on microoptical benches with the dimensions of 13 mm × 4 mm. Reflecting Bragg gratings were used for wavelength stabilization and emission width narrowing. The reliability tests were performed at 25°C and at an output power up to 10 mW per micrometer stripe width of the gain medium. Reliable operation could be demonstrated over a test time up to 14500 h at an output power up to 1.0 W. Environmental tests using random vibrations with acceleration up to 29 g were performed without deterioration of the devices.

Equine wound healing: influence of low level laser therapy on an equine metacarpal wound healing model

AbstractTo evaluate the effects of low level laser therapy (LLLT) on healing of full thickness symmetrical skin wounds in horses. LLLT is a therapeutic modality using the application of light, usually a low power laser or light emitting diode in the power range of 1 mW to 12 W that, in practical terms, promotes tissue regeneration as well as reducing inflammation and pain.Experimental study.Healthy horses (n=8).Full thickness, 2.5 cm square skin wounds were created in the mid-metacarpal region on one leg of eight normal horses. LLLT was used on limbs assigned to the experimental group and limbs assigned to the control group were allowed to heal without treatment. LLLT was administered using a line generated optical scanner with a dual diode laser system (model EML; Erchonia Laser Healthcare, McKinney, TX, USA) at a wavelength of 635 nm and an energy output of 17 mW per diode. Wound size was measured for an 80-day period post operatively. Eighty days after surgery incisional biopsies were examined histologically.Wounds treated with LLLT healed faster than the control wounds (LLLT increased the rate of wound healing.

Intensities and shapes of H2O lines in the near-infrared by tunable diode laser spectroscopy

The integrated intensities, self- and air-broadening coefficients of thirteen transitions of H216O in the 11980–12260cm−1 region, belonging to the 2ν1+ν2+ν3 band, were measured. Using a tunable diode laser system, spectra were recorded at room temperature for a wide range of pressure (2–15Torr for pure H2O and 50–760Torr for H2O in air). Line parameters were adjusted from experiments using three line-shape models: the Voigt profile (VP), the (hard collision) Rautian profile (RP) and the speed dependent Voigt profile (SDVP). The results show that the RP and SDVP are in better agreement with measurements than the VP and that they lead to larger values of the line parameters (about 5% for the line broadening, and 0.8% for the line intensity). Comparisons of the present results with HITRAN 2008 [Rothman et al., JQSRT 2009, 110:533-72] show that the HITRAN intensities of the studied lines are overestimated by about 9.4%, suggesting a more complete study of the H2O line parameters in the considered region. The Dicke narrowing and speed dependence parameters deduced from this work are also presented and discussed, demonstrating the need for a more refined line-shape model.

Chaotic Behavior and Noise-Induced Order in a Laser Diode System with the Feedback Employing Rb Atoms

We experimentally study chaotic fluctuation in a laser diode (LD) system with a feedback loop employing Rb atoms. We find that the LD frequency shows chaotic behavior with a feedback gain. We demonstrate that, by adding the noise to the LD in a chaotic state, a periodic mode of the LD frequency is enhanced. Our results are consistent with those of previous theoretical studies.

Long-term frequency stabilization system for external cavity diode laser based on mode boundary detection

We have realized a long-term frequency stabilization system for external cavity diode laser (ECDL) based on mode boundary detection method. In this system, the saturated absorption spectroscopy was used. The current and the grating of the ECDL were controlled by a computer-based feedback control system. By checking if there are mode boundaries in the spectrum, the control system determined how to adjust current to avoid mode hopping. This procedure was executed periodically to ensure the long-term stabilization of ECDL in the absence of mode hops. This diode laser system with non-antireflection coating had operated in the condition of long-term mode-hop-free stabilization for almost 400 h, which is a significant improvement of ECDL frequency stabilization system.

Multi-threshold second-order phase transition in laser

We present a theory of the multi-threshold second-order phase transition, and experimentally demonstrate the multi-threshold secondorder phase transition phenomenon. With carefully selected parameters, in an external cavity diode laser system, we observe secondorder phase transition with multiple (three or four) thresholds in the measured power-current-temperature three dimensional phase diagram. Such controlled death and revival of second-order phase transition sheds new insight into the nature of ubiquitous secondorder phase transition. Our theory and experiment show that the single threshold second-order phase transition is only a special case of the more general multi-threshold second-order phase transition, which is an even richer phenomenon.

Optical phase dynamics in mutually coupled diode laser systems exhibiting power synchronization

We probe the physical mechanism behind the known phenomenon of power synchronization of two diode lasers that are mutually coupled via their delayed optical fields. In a diode laser, the amplitude and the phase of the optical field are coupled by the so-called linewidth enhancement factor, α. In this work, we explore the role of optical phases of the electric fields in amplitude (and hence power) synchronization through α in such mutually delay-coupled diode laser systems. Our numerical results show that the synchronization of optical phases drives the powers of lasers to synchronized death regimes. We also find that as α varies for different diode lasers, the system goes through a sequence of in-phase amplitude-death states. Within the windows between successive amplitude-death regions, the cross-correlation between the field amplitudes exhibits a universal power-law behaviour with respect to α.

Hair removal utilizing the LightSheer Duet HS hand piece and the LightSheer ET: A comparative study of two diode laser systems in Chinese women

Objective: To compare the clinical efficacy, safety and pain associated with the use of the LightSheer Duet HS as compared to the original LightSheer ET diode Laser for axillae hair removal in Chinese women. Methods: Thirty-six Chinese women received three axillae laser hair removal treatments using the LightSheer Duet HS on one side and the LightSheer ET on the other side. Subjects were evaluated for hair removal efficiency. The immediate pain associated with the treatments was noted. Results: At 1 month following the final laser treatment, hair reduction on the LightSheer Duet HS side and on the LightSheer ET side was 81 ± 13% and 85 ± 9% respectively. There was no statistical difference. Immediate pain scores at the first session on the LightSheer Duet HS sites and LightSheer ET sites was 5.71 ± 1.74 and 6.86 ± 1.80 respectively, which was statistically significant (p < 0.05). Following the second and third sessions, immediate pain scores of the LightSheer Duet HS sites were both less than those of the LightSheer ET sites, but the differences were not statistically significant. Conclusions: The LightSheer Duet HS laser is a safe and effective method of hair removal in Chinese women. Treatment with the LightSheer Duet HS causes less pain.

Miniaturized Tunable External Cavity Diode Laser with Single-Mode Operation and a Narrow Linewidth at 633 nm

A miniaturized, standalone tunable semiconductor laser module operating at a wavelength of 633 nm with a footprint as small as 10 mm × 5 mm is presented. The module is based on an external cavity diode laser system with no moving parts and features a frequency tuning range of 25 GHz with a spectral linewidth of approximately 10 MHz. An output power of 10 mW within a nearly diffraction-limited beam is demonstrated. The electrical power consumption, including thermal management, is around 0.7 W.